Method of forming a clamping ring and a clamping ring

ABSTRACT

For forming a clamping ring first the pipe is extruded. The extruded pipe is cut to form a pipe part. While extruding the pipe, its inner diameter is formed smaller than the outer diameter of a pipe onto which the clamping ring is positioned before making a pipe connection. The inner diameter of the pipe part is made larger by removing material from the inside of the pipe part but only over part of the length of the pipe part such that a stop edge is formed. The clamping ring is used on a pipe when making a pipe connection.

BACKGROUND OF THE INVENTION

The invention relates to a method of forming a clamping ring to be usedon a pipe when making a pipe connection.

Further, the invention relates to a clamping ring to be used on a pipewhen making a pipe connection.

It is known to provide a pipe connection between one end of a pipe madeof a plastic material with memory properties and a connecting piece. Thememory properties mean that plastic pipes with a memory capacityautomatically strive to return essentially to their original shape andform after having been expanded. For example plastic pipes that aremanufactured from cross-linked polyethylene possess an active memorycapacity at temperatures as low as room temperature. Pipes of thisnature are joined together by widening one end of the pipe and insertinginto the widened pipe-end a flanged connector which forms a part of thepipe connecting piece, normally made of metal, and which is retained insaid pipe-end until the pipe has shrunk to an extent at which it is ableto firmly hold the connecting piece. A clamping ring made of elasticmaterial, which may be the same plastic material as that from which thepipe is made, is expanded and shrunk over the pipe end in order tofurther enhance the holding and sealing pressure at the pipe connectionregion. The clamping ring is expanded at the same time as the pipe-endis expanded, with the clamping ring in position around said pipe-end.Such a solution has been disclosed for example in EP 0,530,387. In EP0,530,387 the clamping ring has been made from an extruded pipe bycutting the pipe into a short enough part to form a clamping ring. In WO2007/006,863 the clamping ring is made by injection molding.

BRIEF DESCRIPTION OF THE INVENTION

The object of the invention is to provide a new method of forming aclamping ring and a new clamping ring.

The method of the invention is characterized by: extruding a pipe from aplastic material having memory properties, whereby while extruding thepipe its inner diameter is formed smaller than the outer diameter of thepipe onto which the clamping ring is positioned before making the pipeconnection, cutting the extruded pipe to form a pipe part, making theinner diameter of the pipe part larger by removing material from theinside of the pipe part but only over part of the length of the pipepart such that a stop edge is formed at one end of the pipe part,whereby the pipe part forms the clamping ring.

Further, the clamping ring of the invention is characterized in that theclamping ring is formed from an extruded pipe by cutting the pipe into ashort enough pipe part, which pipe is extruded of a plastic materialhaving memory properties and has an inner diameter smaller than theouter diameter of the pipe onto which the clamping ring is positionedbefore making the pipe connection, and which pipe part has been madelarger by removing material from the inside of the pipe part but onlyover part of the length of the pipe part such that the clamping ringcomprises a stop edge at one end of the pipe part.

In the invention a pipe is extruded. The extruded pipe is cut to form apipe part. While extruding the pipe, its inner diameter is formedsmaller than the outer diameter of a pipe onto which the clamping ringis positioned before making a pipe connection. The inner diameter of thepipe part is made larger by removing material from the inside of thepipe part but only over part of the length of the pipe part such that astop edge is formed. The clamping ring is used on a pipe when making apipe connection. The clamping ring is fast, simple and easy tomanufacture.

In one embodiment the clamping ring is provided with a chamfer on theinlet of the clamping ring. Preferably the chamfer is formed in the samemanufacturing step as the partial widening of the inner diameter. Thechamfer helps in positioning the clamping ring on the end of the pipe inthe pipe connection.

Although the clamping ring is simple, it is provided with a stop edge.The stop edge ensures that the clamping ring remains correctlypositioned on the pipe end when a pipe connection is being made andafter the pipe connection has been made.

BRIEF DESCRIPTION OF THE FIGURES

In the following, the invention will be described in greater detail bymeans of preferred embodiments with reference to accompanying drawings,in which

FIG. 1 schematically shows a pipe connection in cross-section,

FIG. 2 schematically shows a cross-sectional side view of a clampingring, and

FIG. 3 is a schematic representing the steps of making a clamping ring.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a pipe 1, which is comprised of a plastic material havingmemory properties, for instance a cross-linked polyethylene PEX or anyother cross-linked polyolefin, and a connecting piece 2 made of metal.The connecting piece 2 comprises a nipple end 3. The nipple end 3comprises radially projecting flanges 4. The nipple end 3 is terminatedwith a radial abutment surface 5.

The nipple end 3 has an outer diameter which exceeds the inner diameterof the unexpanded pipe 1. An elastic clamping ring 6 is mounted on anend of the pipe 1. In its relaxed state, the clamping ring 6 has aninner diameter which corresponds to the outer diameter of the unexpandedpipe 1.

When establishing the pipe connection shown in FIG. 1, the end of pipe 1and the surrounding clamping ring 6 are expanded simultaneously by anexpander tool. The nipple end 3 is then immediately inserted into theend of the pipe until the abutment surface 5 is in abutment with the endof the pipe 1 and with the clamping ring 6. The end of the pipe 1 andthe clamping ring 6 then shrink or contract automatically, so as toobtain a sealing contact between the inner surface of the pipe and theflange in particular. A sealing contact is also obtained between theinner surface of the pipe 1 and the outer surface of the nipple end 3.

FIG. 2 shows a cross-section of a clamping ring. The outer diameter ofthe clamping ring may vary between 12-150 mm, for example. The length Iof the clamping ring 6 may be e.g. substantially equal to the diameterof the clamping ring. An average wall thickness t_(w) of the clampingring may vary between 2-15 mm, for instance.

The clamping ring 6 is made of cross-linked polyolefin. The clampingring may be made of cross-linked polyethylene PEX or cross-linkedpolypropylene, for example.

One end of the clamping ring 6 is provided with an inward extending stopedge 7. The stop edge 7 is a radially inward protruding continuous ring.The stop edge 7 ensures that the end of the pipe 1 is in a correctposition with respect to the clamping ring 6.

The manufacturing of the clamping ring is illustrated in FIG. 3. First,a pipe is extruded. The extruded pipe has an inner diameter that issmaller than the outer diameter of the pipe 1 onto which the clampingring 6 is positioned before making the pipe connection. After extrudingthe extruded pipe is cut into a short enough pipe part. The innerdiameter of the pipe part is made larger by removing material from theinside of the pipe part. Preferably, the material is removed bymachining the inner surface of the pipe part. Preferably the machiningis performed by a reaming drill. A chamfer is also formed on the inletof the clamping ring 6. The chamfering and the reaming can be made inthe same manufacturing step of the clamping ring 6.

The inner diameter of the pipe is made larger only over part of thelength I of the pipe part. The inner diameter of the pipe part can bemade larger for example in a machining operation that creates a counterbore that bores approximately 95% through the length I of the pipe part.Thus, the counter bore leaves a small edge or lip on the inner diameterof the pipe part. The width w_(s) of the stop edge 7 can be for instance0.3-3 mm depending on the length of the pipe part. The width w_(s) ofthe stop edge 7 can be for example 2-20% of the length I of the pipepart. The original inner diameter D_(o) of the pipe part can be forexample 10-45 mm. The enlarged diameter D_(e) of the pipe part can befor example 0.2-2 mm larger than the original inner diameter D_(o) ofthe pipe part.

Preferably 3-25% of the original extruded wall thickness is removed toachieve the final internal diameter. As an example it can be mentionedthat in one embodiment for an ½ inch ring approximately 0.24 mm of thewall thickness is removed or 7% of the original extruded wall thicknessis removed, on average.

The machining tool that enlarges the inner diameter of the pipe part canbe formed such that it also simultaneously cuts the chamfer 7 on theinlet inner diameter edge of the pipe part. The machining tool can befor example a reaming drill that has a first end that enlarges the innerdiameter of the pipe part and thereafter has a widening part at an angleto the axial direction. The angle to the axial direction is thus theangle of the chamfer and it can be for example between 30-60°. In FIG. 2the angle of the chamfer 8 is 45°.

Preferably the inner surface of the clamping ring is mainly straightwhich means that its direction does not differ from the axial directionof the clamping ring. However, if needed the inner surface of theclamping ring can be made slightly conical. In such a case the coningangle of the inner surface of the clamping ring can be in the range of0.10 to 20, for example.

The size s_(c) of the chamfer can be for example 20-80% of the thicknesst_(w) of the wall.

In some cases the features shown in this description can be used as suchirrespective of other features. Then again the features shown in thisdescription may, if necessary, be combined in order to conform withdifferent combinations.

It is obvious to a person skilled in the art that in the course oftechnical progress, the basic idea of the invention may be carried outin numerous ways. Thus, the invention and its embodiments are notlimited to the previous examples, but they may vary within the scope ofthe appended claims.

The invention claimed is:
 1. A method of forming a clamping ring to beused on a pipe when making a pipe connection, the method comprising:extruding a pipe from a plastic material having memory properties,whereby, while extruding the pipe, its inner diameter is formed smallerthan the outer diameter of the pipe onto which the clamping ring ispositioned before making the pipe connection, cutting the extruded pipeto form a pipe part, making the inner diameter of the pipe part largerby removing material from the inside of the pipe part but only over partof the length of the pipe part such that a stop edge is formed at oneend of the pipe part, whereby the pipe part forms the clamping ring. 2.The method according to claim 1, wherein the material is removed bymachining the inner surface of the pipe part.
 3. The method according toclaim 2, wherein the machining is performed by a reaming drill.
 4. Themethod according to claim 1, wherein a chamfer is formed on an inlet endof the clamping ring.
 5. The method according to claim 4, wherein thechamfer is formed in the same manufacturing step as the removal of thematerial from the inside of the pipe part.